Context Transfer and Common IP Address for DHCP Proxy Solution in WiMAX

ABSTRACT

A network comprising a network component configured with a common internet protocol (IP) address, wherein a similar network component in a similar network is configured with the common IP address, and wherein the network is in communication with the similar network. The disclosure includes a network component comprising a processor configured to implement a method comprising communicating with a mobile station (MS) using an IP address that is common for similar elements in similar networks, and receiving a dynamic host configuration protocol (DHCP) context associated with the MS. Also disclosed is a first access network in communication with a second access network, the first access network comprising a first DHCP proxy configured with a substantially identical IP address as a second DHCP proxy in the second access network, and an agent configured to promote transfer of a DHCP context to the second access network.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/827,839 filed Oct. 2, 2006 by Wu and entitled“Context Transfer and Fixed IP Address for DHCP Proxy Solution InWiMAX”, which is incorporated herein by reference as if reproduced inits entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

An Internet Protocol (IP) address typically comprises a series ofdomains arranged in a hierarchical series. Specifically, an IP addressmay begin with a broad IP domain, which is followed by a plurality ofmore specific IP domains within each preceding domain. When the devicesassociated with IP addresses (IP devices) are relatively stationary, itis possible to determine which networks the IP device is associated withbased on the domains in the IP addresses. Such a hierarchical structureof the IP address aids in routing messages, packets, and other data tothe IP device. If the IP device moves to another network having adifferent IP domain, then the IP device can be issued a new IP addressconsistent with that domain, using a protocol such as dynamic hostconfiguration protocol (DHCP). However, when an IP device is mobile(mobile station (MS)), the issuance of a new IP address to the MS everytime the MS changes networks is an unattractive solution.

One solution to the above problem is to issue the MS a relativelypermanent IP address, such as one associated with the MS's home network,and use the mobile IP (MIP) protocol to tunnel between the MS's homenetwork and the foreign network to which the MS is connected. The MIPprotocol ensures that a moving MS can continue to receive packets whilemaintaining an IP address assigned in a different network.Unfortunately, many MSs do not support MIP. In order to make those MSswithout MIP capability have the same mobility performance as those withMIP capability, WiMAX has designed a Proxy MIP (PMIP) protocol. The PMIPprotocol includes a network entity called a PMIP client that has MIPcapability and conducts MIP operations on behalf of the MS. Since theMSs use DHCP to obtain IP addresses, the PMIP protocol includes anetwork entity called a DHCP proxy that provides the behavior expectedby the MS from a DHCP server.

SUMMARY

In a first embodiment, the disclosure includes a network comprising anetwork component configured with a common IP address, wherein a similarnetwork component in a similar network is configured with the samecommon IP address, and wherein the network is in communication with thesimilar network.

In a second embodiment, the disclosure includes a network componentcomprising a processor configured to implement a method comprisingcommunicating with a MS using a common IP address that is the same forsimilar elements in similar networks, and receiving a DHCP contextassociated with the MS.

In a third embodiment, the disclosure includes a first access network incommunication with a second access network, the first access networkcomprising a first DHCP proxy configured with an identical IP address asa second DHCP proxy in the second access network, and an agentconfigured to promote transfer of a DHCP context to the second accessnetwork.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a schematic diagram of one embodiment of an IP network.

FIG. 2 is a protocol diagram of an embodiment of the DHCP contexttransfer messaging.

FIG. 3 is a flowchart of an embodiment of an IP address assignment andDHCP context transfer method.

FIG. 4 is a flowchart of an embodiment of a DHCP context transfermethod.

FIG. 5 is a schematic diagram of an embodiment of a general-purposecomputer system.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

Disclosed herein is a solution for the situations when an MS moves to anaccess network with a different DHCP proxy. Specifically, disclosedherein is a system and method for utilizing a common IP address for DHCPproxies in a plurality of access networks. By utilizing a common IPaddress for the DHCP proxies in the various access networks, when the MSmoves from a previous access network to a new access network, the MS canuse the DHCP proxy in the new access network without reconfiguring theIP address for the DHCP proxy. Using the DHCP proxy in the new accessnetwork is superior to continuing to use the DHCP proxy in the oldaccess network because DHCP messages from the MS do not need to berouted to the old DHCP proxy.

When using the common IP address for multiple DHCP proxies, collisionsbetween the DHCP messages associated with the common IP address may beavoided by prohibiting the messages associated with the common IPaddress from leaving the access network. Also disclosed is a mechanismfor transferring a DHCP context from the previous access network to thenew access network when the MS moves between the access networks. Theuse of the common IP address and DHCP context transfer may be beneficialin that it facilitates the use of the DHCP proxy in the new accessnetwork rather than maintaining the use of the DHCP proxy in the oldaccess network. This removes the necessity for the DHCP messages fromthe MS to be intercepted and forwarded to the old access network.

FIG. 1 illustrates an embodiment of an IP network 100. The network 100may include A previous access service network (ASN) 102, a connectionservice network (CSN) 104, a new ASN 106, and a MS 109. The CSN 104 maycommunicate directly or indirectly with the ASNs 102, 106, while theASNs 102, 106 may communicate directly or indirectly with each other andthe MS 109. One or both of the ASNs 102, 106 may include a DHCP proxy112 with a common IP address and/or an agent 103.

The MS 109 may be any device that access or communicates, directly orindirectly, with the ASNs 102, 106, and/or the CSN 104. Specifically,the MS 109 may be a wireless device that communicates with the CSN 104,the DHCP proxies 112, the agents 103, and/or other MSs 109 via the ASNs102, 106. The MS 109 may have an IP address assigned to it by one of theASNs 102, 106 or the CSN 104. In a specific embodiment, the MS 109 doesnot support mobile IP (MIP), or may be unable to independently movebetween ASNs 102, 106 without changing its IP address. Examples ofsuitable MSs 109 include personal digital assistants (PDAs), portablecomputers, such as laptop, notebook, and tablet computers, cellulartelephones, and other mobile communication or computing systems. Otherexamples of suitable MSs 109 include other types of computers, such asdesktop, workstation, and kiosk computers using a wireless networkconnection. Alternatively, the MS 109 may be any other type of computeror communication device known to persons of ordinary skill in the art.

The ASN 102, 106 are access networks that provide wireless radio accessto the MS 109. Specifically, the ASNs 102, 106 allows the MS 109 tocommunicate with other users, networks, and devices, such as the CSN104, The previous ASN 102 and the new ASN 106 may be differentiated fromthe perspective of the MS 109 in that the MS 109 was previously incommunication with the previous ASN 102, but has moved such that it isin communication with the new ASN 106. A plurality of the ASNs 102, 106may be associated with a common network access provider (NAP). Inaddition, The ASNs 102, 106 may be associated with more than one CSN104, or each may be associated with different CSNs 104.

The ASNs 102, 106 may perform various functions for the MS 109. Thesefunctions include network connection, radio resource management, ASNanchored mobility, CSN anchored mobility, paging, and ASN-CSN tunneling.ASN anchored mobility refers to mobility within one or more ASNs withoutforeign agent (FA) relocation. FA relocation refers to a process inwhich the MS 109 performs MIP registration with a new FA as a result ofmoving from one ASN 102, 106 to another ASN 102, 106. CSN anchoredmobility refers to a set of procedures associated with the handover ofthe MS between a CSN and an ASN or between an ASN and another ASN, whereFA relocation may be involved. ASN-CSN tunneling refers to theencapsulation of messages that are passed between the ASN and the CSN.

In contrast, the CSN 104 may provide IP connectivity services to IPsubscribers, such as the MS 109. The connectivity services may includeassigning IP addresses to the MS 109, DHCP proxies 112, the agents 103,and/or any other network entities. Such addresses may include permanentor fixed addresses as well as proxy or care-of addresses. Otherconnectivity services include ASN-CSN tunneling support, subscriberbilling, inter-operator settlement, inter-CSN tunneling, inter-ASNmobility, various WiMAX services, and connectivity for peer-to-peerservices, among others. MIP may be implemented between the CSN 104 andthe ASNs 102, 106. In an embodiment, the CSN 104 is part of a networkservice provider (NSP).

The networks 102, 104, 106 may include infrastructure to carry outcommunications with a plurality of devices and networks, such aswireless access points (WAPs), base transceiver stations (BTSs), basestation controllers (BSCs), mobile access gateways (MAGs), localmobility agents (LMAs), routers, switches, bridges, and/or routing logiccircuitry. Specific examples of suitable networks 102, 104, 106 mayinclude one or more of the following networks: the worldwideinteroperability for microwave access (WiMAX), Wireless Fidelity(Wi-Fi), code division multiple access (CDMA), wideband CDMA (WCDMA),orthogonal frequency division multiple access (OFDMA), time divisionmultiple access (TDMA), global system for mobile communications (GSM),enhanced data for GSM evolution (EDGE), universal mobiletelecommunications system (JMTS), advanced mobile phone service (AMPS),one of the Institute for Electrical and Electronic Engineers (IEEE) 802wireless networks, or any other wireless network. In other embodiments,one or all of the networks 102, 104, 106 may be a public switchedtelephone network (PSTN), a packet switched network (PSN), an intranet,the Internet, a local area network (LAN), or any other network known topersons of ordinary skill in the art.

One or more of the networks 102, 104, 106 may contain the agent 103. Theagent 103 may be a network element or functionality that aids inmanaging the MS 109, tunneling packets to other agents in othernetworks, advertising care-of addresses (CoA) that may serve as thetermination point of the tunnel, maintaining current locationinformation for the MS 109, and/or routing messages between the MS 109and the DHCP proxy 112. In a specific embodiment, the previous ASN 102may be a home ASN, and the new ASN 106 may be a foreign ASN. In such anembodiment, the agent in the home ASN may be a home agent (HA), and theagent in the foreign ASN may be a FA.

DHCP is a defined protocol used by networked computers or clients toobtain IP addresses and other parameters such as the default gateway,subnet mask, and IP addresses of domain name system (DNS) servers from aDHCP server. The DHCP server ensures that all IP addresses are unique,e.g., no IP address is assigned to a second client while the firstclient's assignment is valid or its lease time has not expired. DHCPservers provide IP address leases, which typically comprise the IPaddress and an IP address lease time, which may be renewed by the MS 109multiple times.

In an embodiment, the ASNs 102, 106 contain a DHCP proxy that receivesall relevant IP configuration parameters for the MS (e.g., IP address,address lease time, DNS server addresses, etc) from PMIP registration orAAA authentication. The DHCP proxy then interacts with the MS using DHCPprotocol for assigning these IP configuration parameters, as if the MSwere communicating with a DHCP server.

In specific embodiments, the DHCP proxy 112 may be part of a node ordevice, such as an access point (AP), BTS, BSC, NAG, LMAs, or router. Inaddition, the DHCP proxy 112 may be implemented at the same node ordevice in the ASN 102, 106 as the agent 103.

The DHCP proxy 112 may be configured with a common IP address. As usedherein, the term “common IP address” may refer to a source address,destination address, or other designation that is identical for similarnetwork components or elements in similar but different networks. Forexample, the DHCP proxies 112 in ASNs 102, 106 may contain a common IPaddress when both DHCP proxies are configured with the IP address10.10.10.10. The common IP address may be used by the DHCP proxies 112everywhere, by the DHCP proxies 112 within a NAP, by a subset of theDHCP proxies 112 within the NAP, by the DHCP proxies 112 associated witha NSP, by a subset of the DHCP proxies 112 associated with the NSP, orby any other combination of DHCP proxies 112.

The common IP address may be configured using various methods. Forexample, the common IP address may be fixed in that it does not change,or may be dynamic in that it is provided to an MS using networksignaling. The common IP address may be configured either manually orautomatically, as those terms are understood in the art. The common IPaddress may be public in that it is published, advertised, or otherwisemade available to other networks. Alternatively, the common IP addressmay be private in that it is not published, advertised, or otherwisemade available to other networks. Regardless of its configuration, thecommon IP address needs to be made available to the MS 109 in order forthe MS 109 to be able to contact the DHCP proxy 112 upon entry into theASN 102, 106.

In an embodiment, the common IP address may be made known to the MS 109using standard DHCP messages. For example, upon initial network entry,when the MS does not have an IP address, the MS 109 may broadcast a DHCPdiscovery message. The DHCP proxy 112 may respond to the discoverymessage with a DHCP offer message that may include the common IPaddress. Specifically, the DHCP proxy 112 may use the common IP addressas the server identifier and/or the source IP address in the DHCPmessages sent to the MS 109. Once the MS has obtained the conmon IPaddress for the DHCP proxy, it will use this address for as long as ituses its assigned IP address.

Other alternative messages or methods may also be used to make thecommon IP address known to the MS 109. For example, the DHCP proxy 112may periodically broadcast the common IP Address. Alternatively, the MS109 may broadcast a DHCP request message after receiving the DHCP offermessage, and the DHCP proxy 112 may include the common IP address in theDHCP acknowledge message in response to the DHCP request message. Thecommon IP address may make the MS 109 believe that it is communicatingwith the same DHCP proxy regardless of what ASN the MS 109 iscommunicating with, even though the MS 109 is actually conmunicatingwith a completely separate DHCP proxy.

Traditionally, if multiple components contain the same IP address, therewill be collisions in the network. Collisions refer to those cases wherethe routers and other network components do not know which componentoriginated or should receive a message. Collisions may be avoided in thepresent system by prohibiting messages associated with the common IPaddress from leaving the boundary of the network. For the purposesdescribed herein, messages associated with the common IP address includemessages that have the common IP address as the source address or thedestination address, as well as any other messages that may beassociated with the common IP address. As an example, the new ASN 106may be configured with one DHCP proxy 112 having the common IP address.In such a case, messages associated with the common IP address go to ororiginate from the single DHCP proxy 112, and thus there are nocollisions within the ASN 106. In addition, messages associated with thecommon IP address remain in the ASN 106 in that they are prohibited fromgoing to the CSN 104, the ASN 102, or any other network, which preventscollisions outside of the network. Firewalls at the network boundary maybe used to enforce this prohibition on network traffic. In addition, theDHCP proxy 112 may be configured with other, uncommon IP addresses thatmay be used to communicate with entities outside of the DHCP proxy'sASN.

FIG. 2 is a protocol diagram illustrating one embodiment of a method 200for transferring the DHCP context between ASNs. The DHCP context maycontain the IP address assigned to the MS, the IP address lease time,and/or any other information regarding the MS that the previous ASN hasand the new ASN returns. A DHCP context may need to be transferredbetween the previous ASN and the new ASN when the MS moves between theASNs. In a specific embodiment, existing FA relocation messages may beused to achieve the DHCP context transfer. The DHCP context transfer mayallow the handover between the agents 103 and the DHCP proxies 112 inthe previous ASN 102 and the new ASN 106 to occur substantiallysimultaneously. Stated differently, the agent 103 and the DHCP proxy 112may relocate access networks together.

At 201, the new ASN may initiate the DHCP context transfer. The new ASNmay initiate the DHCP context transfer, for example, upon recognitionthat the MS has entered the new ASN or upon receipt of a message fromthe MS. The DHCP context transfer may be initiated by sending aninitiation message to the previous ASN. In a specific embodiment, theinitiation message is an existing FA relocation message.

If the previous ASN agrees to the DHCP context transfer, the previousASN may respond with the DHCP context at 202. Alternatively, if theprevious ASN is aware of or can predict which ASN the MS is going to,the previous ASN may initiate the DHCP context transfer at 202. Ineither case, the response may comprise a message, packet, or other datastructure that contains the DHCP context described above. The responsemay also comprise other information, such as the common IP address, anauthenticator ID, or any other information. In a specific embodiment,the response message is an existing FA relocation response message.

At 203, the new ASN may register with the MS's home network.Specifically, the new ASN may send a message to the home network toinform the home network that any messages, packets, or other datadestined for the MS should be directed to the new ASN. The message maycontain the MS's IP address, the agent in the previous and/or new ASN,or a proxy MIP client in the previous and/or new ASN. In a specificembodiment, the message may be a MIP relocate request (RRQ) message. At204, the home network may respond with a confirmation of the new ASN'sregistration. Such a confirmation message may be in the form of aregistration request response (RRR).

In an alternative embodiment, the previous ASN may register the new ASNwith the home network. Specifically, the previous ASN may send a messageto the home network informing the home network of the movement of the MSfrom the previous network to the new network. Such a message may containany of the information identified above. The home network may thenoptionally respond to the previous ASN, the new ASN, or both.

At 205, the new ASN confirms that the DHCP context transfer wassuccessful. The confirmation may allow the previous ASN to release anyresources dedicated to the MS, and may absolve the previous ASN of anyfurther responsibility towards the MS. In a specific embodiment the newASN may confirm the DHCP context transfer using an existing FArelocation message.

FIG. 3 illustrates one embodiment of a method 300 for assigning a commonIP address to a DHCP proxy. The method 300 may include provisioning thecommon IP address at 301. Provisioning the common IP address may involveprovisioning the common IP address into the routing table of the routeror other component associated with the DHCP proxy. Provisioning thecommon IP addresses may be accomplished via a network management system,a routing protocol, or combinations thereof. Specifically, the networkmanagement system may allow an operator to provision the common IPaddress into each ASN in a NAP's domain. The method 300 may also includepropagating the common IP address at 302. Propagating the common IPaddress may involve using a routing protocol, such as internet controlmessage protocol (ICMP) router discovery protocol, to help propagate thecommon IP address to routers in the ASNs of the NAP.

FIG. 4 illustrates one embodiment of a method 340 for transferring aDHCP context during FA relocation. The method 340 may include embeddingthe DHCP context into an existing relocation message at 341. Uponcompletion of the embedding, the previous ASN may send the requestmessage to the new ASN at 342. The new ASN may then use the DHCP contextinformation to perform any mobility related functions for the MS. Thenew ASN may also send a response message to the previous ASN to indicatethat the DHCP context transfer is complete.

While the methods and systems described herein have been illustratedusing the DHCP proxy, the methods and systems described herein may beapplied to other IP devices as well. For example, the common IP addressmay be used for any network component that is substantially the same ina plurality of networks such that the use of the common IP address mayreduce signaling, aid in handover, or may otherwise be beneficial. Forexample, it is contemplated that the agents described herein may also beassociated with a common IP address, albeit one that is separate fromthe common IP address used for DHCP proxies. Persons of ordinary skillin the art are aware of other network components that may benefit fromuse of the common IP address.

The network described above may be implemented on any general-purposenetwork component, such as a computer or network component withsufficient processing power, memory resources, and network throughputcapability to handle the necessary workload placed upon it. FIG. 5illustrates a typical, general-purpose network component suitable forimplementing one or more embodiments of a node disclosed herein. Thenetwork component 400 includes a processor 402 (which may be referred toas a central processor unit or CPU) that is in communication with memorydevices including secondary storage 404, read only memory (ROM) 406,random access memory (RAM) 408, input/output (I/O) 410 devices, andnetwork connectivity devices 412. The processor may be implemented asone or more CPU chips, or may be part of one or more applicationspecific integrated circuits (ASICs).

The secondary storage 404 is typically comprised of one or more diskdrives or tape drives and is used for non-volatile storage of data andas an over-flow data storage device if RAM 608 is not large enough tohold all working data. Secondary storage 404 may be used to storeprograms that are loaded into RAM 408 when such programs are selectedfor execution. The ROM 406 is used to store instructions and perhapsdata that are read during program execution. ROM 406 is a non-volatilememory device that typically has a small memory capacity relative to thelarger memory capacity of secondary storage. The RAM 408 is used tostore volatile data and perhaps to store instructions. Access to bothROM 406 and RAM 408 is typically faster than to secondary storage 404.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

1. A network comprising: a network component configured with a commoninternet protocol (IP) address, wherein a similar network component in asimilar network is configured with the common IP address, and whereinthe network is in communication with the similar network.
 2. The networkof claim 1, wherein the network component is a dynamic hostconfiguration protocol (DHCP) proxy.
 3. The network of claim 1, furthercomprising an agent configured to promote the transfer of a DHCP contextto a similar agent in the similar network.
 4. The network of claim 3:wherein the network component is a dynamic host configuration protocol(DHCP) proxy associated with a mobile station (MS), wherein the agent isassociated with the MS, and wherein the agent and the DHCP proxyrelocate substantially simultaneously.
 5. The network of claim 4,wherein the MS does not support mobile IP,
 6. The network of claim 1,wherein the network is a worldwide interoperability for microwave access(WiMAX) network.
 7. The network of claim 1, wherein the IP address ispublic.
 8. The network of claim 1, wherein the network is configuredsuch that any packets or messages containing the common IP address as asource address or a destination address are prohibited from leaving thenetwork.
 9. The network of claim 1, wherein the network component isconfigured to communicate with a mobile station (MS) using the common IPaddress.
 10. The network of claim 9, wherein the network component isconfigured to use the common IP address as the source IP address in amessage sent to the MS.
 11. A network component comprising: a processorconfigured to implement a method comprising: communicating with a mobilestation (MS) using an internet protocol (IP) address that is common forsimilar elements in similar networks; and receiving a dynamic hostconfiguration protocol (DHCP) context associated with the MS.
 12. Thenetwork component of claim 11, wherein the DHCP context is receivedusing a foreign agent relocation message.
 13. The network component ofclaim 11, wherein the IP address is used exclusively by a plurality ofDHCP proxies.
 14. The network component of claim 11, wherein the MS doesnot support mobile IP.
 15. A first access network in communication witha second access network, the first access network comprising: a firstdynamic host configuration protocol (DHCP) proxy configured with asubstantially identical internet protocol (IP) address as a second DHCPproxy in the second access network; and an agent configured to promotetransfer of a DHCP context to the second access network.
 16. The firstaccess network of claim 15, wherein the first DHCP proxy communicateswith a mobile station (MS) that does not support mobile IP.
 17. Thefirst access network of claim 15, wherein the first access network andthe second access network belong to a single network access provider.18. The first access network of claim 15, wherein the DHCP contextcomprises a mobile station IP address and a mobile station IP addresslease time.
 19. The first access network of claim 15, wherein the firstaccess network comprises only one DHCP proxy.
 20. The first accessnetwork of claim 15, wherein the DHCP proxy and the agent areimplemented at a common node.